(a) Field of the Invention
The present invention relates to a spot welding apparatus, and more particularly, to a spot welding apparatus that performs a welding operation by selecting a lower welding gun that matches a welding spot of a welding target to be universally applied to multiple car models and enable a rapid welding operation in a limited space with a minimum time period.
(b) Description of the Related Art
In general, during a manufacturing process of a vehicle, various structural parts such as a vehicle body panel molded by a press, and the like are bonded by a method such as welding to complete an integrated vehicle body. The completed vehicle body is painted and rust-prevention is applied throughout the surface of each part in a painting process. Thereafter, a design process is performed, such as assembling a part of a power train system and parts such as suspension, steering, and braking systems and subsequently, assembling a door and a trunk lid, a hood, and the like.
Further, in a vehicle body assembling process of the vehicle, spot resistance welding through a spot welding apparatus is frequently used as a method for bonding two vehicle body panels such as a roof, a pillar, a side panel, an opening unit flange of a vehicle body door, and the like.
The spot resistance welding is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current. As such, the weld is typically made by holding work-pieces together under pressure exerted by electrodes. via a spot welding apparatus installed at an arm front end of a robot for spot welding.
A welding gun used in spot welding apparatus are divided into three types: an X-type welding gun, a C-type welding gun, and a special-type welding gun adopting a special lower arm according to the position of a welding portion and interference with the vehicle body.
One spot welding apparatus selectively adopting the X-type welding gun, the C-type welding, and the special-type welding gun is installed through an arm of a robot. As a result, a first robot in which the spot welding apparatus adopting the X-type welding gun is installed, a second robot in which a spot welding apparatus adopting the C-type welding gun is installed, and a third robot in which a spot welding apparatus adopting the special-type welding gun is installed are installed in sepaaratelyto achieve the appropriate spot welding operations.
However, in the conventional spot welding operation, since one spot welding apparatus is installed in the robot arm for each robot, only one spot is welded whenever the robot arm moves, and as a result, a lot of time is required to perform a predetermined number of welding spot operations, thereby degrading productivity and efficiency.
Further, lower welding guns having different shapes should be adopted according to the position and the shape of the welding spot, and as a result, facility investment costs increase, and in particular, when a plurality of robots mounted with a spot welding apparatus adopting a lower welding gun having a special shape is used, facility and maintenance costs increase and energy is excessively used. Additionally, a space occupancy rate of the robot in a mass production line also increases.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.